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C4.1: Density

C4.1: Density. Physical Science. C4.1 Density. Supplies: A pencil and science notebook Standards: 8a) Density is mass per unit volume 8b) Calculate the density of substances from measurements of mass and volume 9f) Apply simple mathematic relationships to determine a missing quantity.

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C4.1: Density

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  1. C4.1: Density Physical Science

  2. C4.1 Density • Supplies: A pencil and science notebook • Standards: • 8a) Density is mass per unit volume • 8b) Calculate the density of substances from measurements of mass and volume • 9f) Apply simple mathematic relationships to determine a missing quantity

  3. C4.1 Density • You will be taking notes using Cornell Notes format or Charting Notes format.

  4. C4.1 Density • Definitions • Density: the mass of matter per unit volume; density is typically expressed in units of grams per milliliter (g/mL), grams per cubic centimeter (g/cm3), or kilograms per cubic meter (kg/m3).

  5. Density is a property of matter • Population density? • Forest density? • Density of stars? • Air quality?

  6. Density in Physics • Density is a property of matter, like color or size. • Density is mass per unit volume. • Given a cubic centimeter of • Steel • Water • Air • Which has more mass?

  7. Units of density • Units are g/cm3 • Ratio means • 1 g/cm3 = 1000 kg/m3 • Steel at 8.7 g/cm3 is 8,700 kg/m3 (multiply by 1000 and change units.) • Oak at 600 kg/m3 is 0.60 g/cm3 (divide by 1000 and change units.) • How does the density of oak compare to the density of water?

  8. Solving problems • D=m/v • Solve for m • Solve for v

  9. Solve it • A stainless steel sphere has a mass of 25 grams and a volume of 3.2 cm3. What is the density of the sphere? • A cube has a mass of 7.8 grams. The length of the sides of the cube is 1.2 cm. What is the density of the cube?

  10. Solve it, then compare • Honey’s density is 1.4 g/cm3 • Write this as kg/m3 • Sandstone’s density is 20,280 kg/m3 • Write this as g/cm3 • Compare answers with with someone nearby.

  11. Density Samples

  12. Use a balance to find the mass Use a graduated cylinder to find the volume (not a beaker – why?) D = mass/volume Determining Density

  13. Using a graduated cylinder • Read the mark at eye level • Read volume at center of meniscus (ask your teacher!) • 1 mL = 1 cm3

  14. Volume of solids • Length X width X heights gives cubic centimeters • What is the volume of a box that is 10” long, 5” wide, and 3” high? • What is the volume of a box that is 2’ long, 1’ wide, and 9” high?

  15. More volumes, use 3.14 for π • Sphere: V=(4/3)πr3 • What is the volume of a sphere with a radius of 2 cm? • Cylinder: V=πr3h • What is the volume of a cylinder that is 10 cm tall and has a radius of 3 cm?

  16. Irregular shapes • Volume by displacement of fluid • Remember: 1 mL = 1 cm3 • Fill graduates cylinder with fluid to known level (50 mL) • Carefully slide object down the side of the cylinder • Compute the increase in the fluid height • 82 mL - 50 mL = 32 mL • 32 mL = 32 cm3

  17. Compute this • I fill a graduated cylinder with 50 mL of water. • I slip a stone into the cylinder and the water raises to 62 mL. • What is the volume of the stone?

  18. Why density varies • Mass of each atom or molecule that that makes up the substance – a calcium atom has more ‘stuff’ in it than an oxygen atom. • How tightly the atoms are packed -- the atoms are closer together in diamond that in graphite, but both are carbon. • (Except for water) solids are more dense than liquids • Liquids are more dense than gases

  19. Ticket Out: Answer this • Which has more mass, a pound of bricks or a pound of feathers? • Which is more dense, a pound of bricks or a pound of feathers.

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